Overclocking CPU and overclocking RAM is 2 totally separate things. When overclocking, there's a few major components:
CPU
CPU-NB aka memory controller, imc, etc (systems with bclk like intel don't let you change this)
HT Link Speed (not to be confused with ht link reference or whatever, i think this is just amd and there's no need to change this except maybe if you got like 3 gpus, even then i dont think it's necessary)
RAM (both speed and timings)
GPU
Generally, overclocking one doesn't really affect the others (although it can for cpu-nb and ram). You also overclock each on it's own, so like set everything to stock, crank up cpu. Once you got that dialed in, overclock your RAM (if you care to, cpu and gpu are really the big things to overclock) to as far as you can get it (for each step up in speed, ie 1333mhz to 1600, 2000mhz to 2133mhz, try not to loosen ram more than one for each major timing, ie 2000 CL8-8-8-24 > 1866 CL9-9-9-26 but not by much at all). Then overclock GPU. They all work independently.
You dont need to increase ram with cpu, or ram with cpu. But it is nice to overclock both of them. So see what your CPU can do, once you figure that out, say 4.5ghz, keep it at that, and then increase ram. Or, keep cpu at stock and play with ram, then make sure both are stable together (like i said, they usually don't limit eachother but i mean sometimes you might have something going on, you always want to test for total system stability). CPU first because it's the most important (ie 4ghz 1333mhz >>>> 3.9ghz 2000mhz ram).
If you have a K edition CPU there's no reason not to overclock to 4.5ghz-5.1ghz. A locked Cpu can be overclocked to 4ghz, it would be silly to do such a minor overclock. It depends on what you do, if you play a non-cpu intensive game like crysis then cpu overclock isn't a big deal, gpu overclock is really what is important, but if you play cpu intensive games like starcraft, total war, then yea it makes a huge difference to go from 4ghz to 4.2ghz. Personally I both play and stream my games, and streaming is extremely cpu intensive, not to mention the games I play are very hard on the cpu, particularly single threaded performance (ie speed over core count), so every 100mhz is noticeable to me.
If I were you, on a new chip, I'd see if I can do like
[email protected], a very conservative overclock on a good overclock (ie good chips that can do more will pass it, bad chips won't). You really want to get 24 hours passed on stock to make sure there is nothing faulty in your system (all faulty hardware I've ever had that I had to rma, could pass at least 12 hours of prime95, and then would fail at like 14+ hours). You just want to see the limits of your chip. Just write down every frequency and voltage you do, compare to results in the OC clubs and online and such, see what your chip can do.
Like I tested
[email protected], a fairly high voltage for chips good enough to do 4.8, but just to make sure this chip was good. Then I tried
[email protected], it failed, so then I tested
[email protected], it passed. I also played with the ram, it was stock 2000 mhz CL7-10-8-27 1.65v. I try 2400mhz, nope, had to loosen timings to 8-12-8-28 1.75v, it could pass like an hour of p95, I keep playing with tightening the lesser timings, try less voltage, that wouldn't work, eventually I figured out how tight I could get the secondary and tertiary timings, now I run p95 again for 24 hours, see if I can do 8/12/8/28 @ 1.75v with the secondary and tertiary timings set to a particular level.
It's all about how much time and effort you are willing to put into it. You get diminshing returns, like cpu clock is a big deal, but after that ram overclocking really isn't huge (for me it's noticeable, not as noticeable as 100mhz but still a big deal). You can play around and go as far as testing how far you can get trfc, nope 90 isn't stable, try 98, try 133, i mean it's up to you how fine tuned you want to make it all.
